Heretofore, conventional type drill rod systems have generally utilized a plurality of hollow drill rod members which are typically coupled together in end-to-end relation for removing particulate materials away from the cutting area upon application of a vacuum to the system. In such systems, a drill bit is detachably connected adjacent the working end of the last drill rod and typically has dust-collection openings formed therein which communicate with the interior of the hollow drill rods for removing the drill cuttings from the drill area by the provision of a negative pressure differential between the interior and exterior of the drill rod members upon application of a vacuum to the system, as aforesaid. The other end of the drill rod system is typically connected to a power driven chuck for rotating the drill rod system in a manner known in the art.
In prior drilling systems severe problems have developed in respect to damage and/or wear between the coupled and abutting drill rod members and/or between one of the drill rod members and the drive chuck and/or drill bit. Particular problems have been encountered in respect to the driving connection between the respective drill rod member and the drill bit due to the relatively heavy thrust load forces transmitted from the drill rods to the cutting bit. These load forces are developed not only from a rotary action on the drill bit but also due to the axial, reciprocating action on the drill rod members which imparts a "hammering" action on the drill bit. For example, it has been found that a severe axial thrust force acts to drive the drill rod in some instances into the hollow body of the drill bit causing splitting of the drill bit and/or resulting in an actual "welding" of the drill bit to the associated drill rod. In addition, it has been found that as the component parts wear down adjacent the areas of their connections to one another so that the system tends to lose its rigidity resulting in a "wobbling" action rendering it difficult for the operator to carry out the drilling operation. Such loosening between the component parts of the system not only renders the drilling operation difficult but also tends to creat a hazardous condition for the operator especially because of the relatively high thrust loads necessary for drilling hard strata.